The present invention relates to the field of power and energy, and energy conversion, in particular, to direct methanol fuel cells (DMFC) and batteries comprising a nanostructure biomimetic electron-relay membrane electrode assembly (MEA).
Due to the danger and high cost for storage of liquid hydrogen as fuel cell, more and more people are interested in developing fuel cells that are less dangerous and less costly due to their storage of hydrogen. Proton Exchange Membrane Fuel Cells (PEMFCs) have been a candidate for powering the next generation of vehicles with their efficiency, low-noise power, and ability to operates at 70-100° C. The Polymer Electrolyte Membrane (PEM) fuel cell has a fluorinated polymeric membrane, which allows hydrogen ions (protons) to pass through it. The membrane is coated on both sides with highly dispersed metal alloy particles (mostly platinum) that are active catalysts. The PEM cell appears to be more adaptable to automobile use.
The cost of fuel cells hinders competition in widespread domestic and international markets which do not have significant government subsidies. According to the Business Communications Company, the market for fuel cells was about $218 million in 2000 and will reach $7 billion by 2009 (21th Renewable Energy data Book, 2005, U.S. Government). PEMFCs currently cost several thousand dollars per kW.
The conventional approaches in fuel cell developments use fuels (either hydrogen or alcohol) as reactants taken in an oxidation reaction at the anode, and a reduction reaction of oxygen at the cathode, using a platinum catalyst. Various electrolytes have to be used in order to carry the charged ions to the surface of the electrodes, thereby causing the fuel cell to function. The overwhelming effect of over-potentials caused by: (1) proton migration; (2) the two-phase, (liquid (fuel)-gas (oxygen, CO2)) mass diffusion; and (3) the flow of fuel to the surface of the MEA (i.e., convection fuel flow over-potential) in the fuel cell have been previously reported (See, A. J. Bard and L. R. Faulkner, Electrochemical Methods, Fundamentals and Applications, John Wiley & Sons, New York, (1980); P. T. Kissinger and W. R. Heineman, Laboratory Techniques in Electroanalytical Chemistry, Second Edition, Marcel Dekker, New York, (1996); W. P. Liu, C. Y. Wang, J. Power Sources, 164:189 (2007); T. Bewer, et al., J. Power Sources, 125:1, (2004); Chao Xu, Ph.D. Dissertation: “Transport phenomena of methanol and water in liquid feed direct methanol fuel cells”, The Hong Kong University of Science and Technology, (2008).
The Direct-Methanol Fuel Cell (DMFC) is similar to the PEM cell, in that it uses a polymer membrane as an electrolyte. However, a catalyst on the DMFC anode draws hydrogen from liquid methanol, eliminating the need for a fuel reformer. The major scientific challenges facing current PEMFC and conventional DMFC technology are: (1) low efficiency; (2) the conventional DMFC cell suffers from being irreversibly hydrodynamic due to the by-products of CO2 and water; (3) energy loss due to the hydrophobic polymer electrolyte membrane being the only means to promote the DMFC function, which limits this technology because water floods the membrane electrode assembly (MEA); (4) the CO2 produced as a by-product also causes malfunction of the membrane; (5) methanol crossing over the membrane; and (6) the danger of a dry Nafion® membrane, which becomes extremely explosive and toxic, hence requiring a humidifier to moisture the MEA in order to avoid the dangerous dryness.
Because of the drawbacks of current technologies driving fuel cell development, the goal of the present invention is to develop a revolutionary approach that overcomes the drawbacks associated with the current technology and create new fuel cells and batteries offering a magnitude increase in fuel cell performance with possible outcome of reducing cell cost.